The Pregnancy Core (Core B) will provide murine and rhesus gametes, embryos and staged pregnancies (both control and manipulated) to SCOR investigators for investigations on early embryogenesis, imprinting genes critical to implantation, skewed X-inactivation, inflammation during pregnancy loss, smoking during pregnancy, and pregnancy monitoring using non-invasive imaging techniques. The facility provides expertise on ovarian stimulation, in vitro fertilization (1VF), and intracytoplasmic sperm injection (ICSI), embryo culture, twinning, and embryo transfer for pregnancy establishment, artificial insemination and transgenic approaches for deriving genetically modified offspring. For primates, we principally utilize rhesus monkey oocytes and employ these various techniques to evaluate the fertilizing capacity of sperm, produce embryos at specific stages of preimplantation development and of different genetic reconstitution, and produce transgenic embryos for pregnancy establishment. The Core will provide fertilized rhesus monkey zygotes at the pronuclear stage for transgene infection and cultured embryos for twinning and embryo transfer for pregnancy establishment. Frozen embryos at all stages of preimplantation development are also available to augment the production of fresh material. The Core conducts macaque embryo transfers, both transcervically (non-surgical) and oviductally via laparotomy and establishes timed pregnancies for use in fetal development studies. For mice, we routinely provide gametes, embryos at differing stages, manipulated embryos and timed pregnancies, as well as establishing genetically modified mouse lines. Timed pregnancy establishment for use in non-invasive imaging technologies like MRI and PET analysis (as described in Core A) will also be available for SCOR investigators. Core B )rovides high quality, cost-effective service for Research Projects I, II and III.